*{
    margin: 0;
    padding: 0;
}

.div1{
    width:800px;
    height:800px;
    background-color: aqua;
}
.box1,.box2,.box3,.box4{
    height:200px;
    width: 200px;
}
.box1{
    background-color: red;
}
.box2{
    background-color: blue;
}
.box3{
    background-color: green;
}
.box4{
    background-color: yellow;
}